JP2008179300A - Rollover suppression control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform rollover suppression control with the behavior of a vehicle being stable while ensuring the tire grip force during a turn without using a braking system. <P>SOLUTION: The roll angular acceleration ϕa calculated based on the roll rate ϕv applied to a vehicle body is compared with the threshold α to determine whether or not the roll state of the vehicle body is a suddenly changing abrupt roll state (S8). If the abrupt roll state is determined, the roll rate ϕv is compared with the threshold β to determine whether or not any rollover is predicted (S16). When it is determined that the rollover is predicted, the corrective assist quantity τasist is obtained based on the roll rate ϕv (S23). The corrective assist quantity τasist is subtracted from the basic assist quantity τ obtained based on the steering torque Tq and the vehicle speed Vsp to calculate the target assist quantity τa (S24, S25). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rollover suppression control device for a vehicle that, when a rollover sign is detected, reduces an assist amount generated by driving an assist actuator that assists steering torque to avoid rollover.

  Generally, when a running vehicle turns sharply or enters a corner at an overspeed, a large lateral acceleration (centrifugal force) acts on the vehicle, and the vehicle tilts outward in the turning direction. At that time, if the lateral acceleration is excessive and it becomes difficult to return the vehicle tilt posture, rollover (rollover) is caused.

  For this reason, various techniques for avoiding rollover during turning have been proposed. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2005-104340) discloses a technique for avoiding rollover by using a braking system installed in a vehicle.

  That is, in this document, (1) when the vehicle speed, lateral acceleration, and roll rate during turning are equal to or higher than a reference value, control is performed to apply a braking force corresponding to the roll rate to the turning outer wheel to avoid rollover ( Roll rate control).

  (2) When the vehicle speed and lateral acceleration at the turn are equal to or higher than other reference values, control is performed to apply a braking force corresponding to the lateral acceleration to the turning outer wheel to avoid rollover (lateral acceleration control).

(3) When both roll rate control and lateral acceleration control are activated, a control amount obtained by weighting and adding each control amount calculated in roll rate control and lateral acceleration control is obtained, and rollover is avoided with the control amount. Control.
JP 2005-104340 A

  However, the technique disclosed in the above publication cannot be applied to a vehicle that is not equipped with a braking system.

  Further, when braking force is applied to the turning outer wheel during turning, there is a problem that the tire grip force of the turning outer wheel is reduced and the vehicle behavior is likely to become unstable.

  By the way, it is known that the rollover is caused by abrupt steering at the start and return of steering. In the case of such a sudden steering, if the steering is so large that the turning inner wheel is lifted, there is a possibility that rollover cannot be avoided due to a delay in starting the control.

  For example, when a steering operation such as a fish hook turn is performed, the turning direction is continuously largely switched, so that the vehicle body rolls back, and the resonance phenomenon causes the inner wheel to turn before the lateral acceleration is detected. Floating easily occurs. As a result, there is a disadvantage that the grip force of the tire is lowered and rollover cannot be sufficiently avoided.

  In view of the above circumstances, the present invention can be applied to a vehicle that is not equipped with a braking system, and sufficiently suppresses and controls rollover in a state where the tire grip force during turning is ensured and the vehicle behavior is stabilized. It is an object of the present invention to provide a vehicle rollover suppression control device that can prevent the control start delay when the vehicle is steered rapidly.

  In order to achieve the above object, a rollover suppression control device for a first vehicle according to the present invention includes an assist actuator that assists a steering torque applied to a steering wheel, a roll rate detection means that detects a roll rate of a vehicle body, and the steering torque. A steering torque detection means for detecting a basic assist amount based on at least the steering torque detected by the steering torque detection means and a target assist amount for driving the assist actuator by correcting the basic assist amount And a control means for calculating the roll angular acceleration of the vehicle body based on the roll rate, and an abrupt change in which the roll state of the vehicle body rapidly changes based on the roll angular acceleration. Low to determine whether the roll state or a slow roll state that changes slowly. A state determination unit, a roll rate determination unit that compares the roll rate and a roll rate threshold value to determine whether or not there is a sign of rollover, and the roll state determination unit determines a sudden roll state; and When the roll rate determining means determines that there is a sign of rollover, a sudden roll correction assist amount calculating means for calculating a correction assist correction amount for correcting the target assist amount in a direction to decrease based on the roll rate; And a sudden roll target assist amount calculating means for calculating the target assist amount by correcting the basic assist amount with the correction assist amount.

  A second vehicle rollover suppression control device includes an assist actuator that assists a steering torque applied to a steering wheel, a roll rate detection unit that detects a roll rate of a vehicle body, a steering torque detection unit that detects the steering torque, A lateral acceleration detecting means for detecting a lateral acceleration of the vehicle body, a target for calculating a basic assist amount based on at least the steering torque detected by the steering torque detecting means, and correcting the basic assist amount to drive the assist actuator Control means for setting the assist amount, the control means for calculating the roll angular acceleration of the vehicle body based on the roll rate, and the roll state of the vehicle body rapidly based on the roll angular acceleration. Whether it is a sudden roll state that changes slowly or a slow roll state that changes slowly. A roll state determination unit that determines whether there is a sign of rollover by comparing the roll rate with a roll rate threshold value, and the roll state determination unit determines that the roll state is a sudden roll state. And when the roll rate determination means determines that there is a sign of rollover, the lateral acceleration and the lateral acceleration threshold value are compared to further determine whether or not there is a sign of rollover. When the lateral acceleration determining means determines that there is a sign of rollover, a rapid roll correction assist amount calculating means for calculating a correction assist correction amount for correcting the target assist amount in a direction to decrease based on the roll rate. And a sudden roll target assist amount calculation means for calculating the target assist amount by correcting the basic assist amount with the correction assist amount. Characterized in that it comprises a.

  According to the present invention, the target assist amount for assisting the steering torque is reduced when a rollover sign is detected when the roll state of the vehicle body is determined to be the sudden roll state. It can be applied to a vehicle not equipped with a vehicle, and not only can excellent economic efficiency be obtained, but also can be incorporated into an existing system, so that high versatility can be obtained.

  Compared to the conventional technology that avoids rollover by braking the wheel, the tire grip force during turning can be secured, and rollover can be sufficiently suppressed and controlled while the vehicle behavior is stabilized. Can do. Further, after the sudden roll is detected, the target assist amount is greatly reduced, so that it is possible to prevent a delay in starting the control when sudden steering is performed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a vehicle equipped with a rollover suppression control device.

  Reference numeral 1 in the figure denotes an electric power steering device. A steering shaft 2 of the electric power steering device 1 is rotatably supported by a vehicle body frame (not shown) via a steering column 3, and one end thereof is on the driver's seat side. The other end is extended to the engine room side. A steering wheel 4 is fixed to the end of the steering shaft 2 on the driver's seat side, and a pinion shaft 5 is connected to the end extending to the engine room side.

  A steering gear box 6 extending in the vehicle width direction is disposed in the engine room, and a rack shaft 8 is inserted into and supported by the steering gear box 6 so as to be reciprocally movable. A rack (not shown) formed on the rack shaft 8 is engaged with a pinion formed on the pinion shaft 5 to form a rack and pinion type steering gear mechanism. The left and right ends of the rack shaft 8 protrude from the end of the steering gear box 6, and a front knuckle 10 is connected to the end via a tie rod 9. The front knuckle 10 rotatably supports left and right wheels 11L and 11R as steering wheels, and is supported by a vehicle body frame via a king pin (not shown) so as to be steerable. Therefore, when the steering wheel 4 is operated and the steering shaft 2 and the pinion shaft 5 are rotated, the rack shaft 8 is moved in the left-right direction by the rotation of the pinion shaft 5, and the front knuckle 10 is moved by the movement to the king pin (not shown). ) And the left and right wheels 11L and 11R are steered in the left-right direction.

  Further, an electric motor 13 as an assist actuator is connected to the pinion shaft 5 via an assist transmission mechanism 12, and the steering torque applied to the steering wheel 4 is assisted by the electric motor 13. Further, a steering torque sensor 14 as a steering torque detecting means is connected to the steering shaft 2, and the steering torque applied to the steering wheel 4 is detected by the steering torque sensor 14.

On the other hand, reference numeral 21 denotes a motor control unit as a control means for controlling the driving of the electric motor 13. On the input side of the motor control unit 21, a steering torque sensor 14 for detecting the steering torque Tq applied to the steering wheel 4, a vehicle speed sensor 15 for detecting the vehicle speed Vsp, and a lateral acceleration Gy [m / s ² ] of the vehicle body are detected. A lateral acceleration sensor 16 serving as a lateral acceleration detecting means and a roll rate sensor 17 serving as a roll rate detecting means for detecting a roll rate φv acting on the vehicle body are connected. In the present embodiment, the lateral acceleration Gy and the roll rate φv that are generated when the vehicle turns to the left in the normal traveling without positive turning are positive (+), the lateral acceleration Gy that is generated when the vehicle turns to the right, and the roll rate. φv is expressed as a negative value (−).

  As shown in FIG. 2, the motor control unit 21 includes a motor control unit 22, a motor drive signal generation circuit 23, a motor drive circuit 24, and a current detection unit 25 as a function for assisting the steering torque.

  The motor control unit 22 is mainly composed of a microcomputer, and has a nonvolatile storage means such as a well-known CPU, ROM, RAM, and EEPROM. This motor control unit 22 detects a sign of occurrence of rollover, that is, a behavior leading to rollover, according to a control program stored in the ROM, calculates a correction assist amount τasist corresponding to the roll rate φv, The basic assist amount (torque) τ set based on the steering torque Tq detected by the steering torque sensor 14 is corrected with the corrected assist amount τaist to calculate the target assist amount (torque) τa.

  Then, a target assist current P that is a target value of the current (assist amount) supplied to the electric motor 13 corresponding to the target assist amount τa is set, and the target assist current P and the motor detected by the current detection unit 25 are set. A difference ΔP with respect to the current Is is calculated, and based on the difference ΔP, a control signal (feedback control signal) D such that the difference ΔP converges to 0 is generated by a known proportional-integral control calculation or the like.

  The motor drive signal generation circuit 23 generates a motor drive signal corresponding to the feedback control signal D. In addition, as this motor drive signal, there exists a pulse width modulation signal (PWM signal) of the duty ratio according to the control signal D, for example.

  The motor drive circuit 24 outputs a voltage corresponding to the motor drive signal to the electric motor 13. The current detection unit 25 detects a current (motor current) Is supplied to the electric motor 13 and outputs it to the motor control unit 22.

  Specifically, the processing in the motor control unit 22 described above is performed according to the routines shown in FIGS. When an ignition switch (not shown) is turned on, a roll angular velocity flag setting routine shown in FIG. 3 is executed every setting calculation cycle (1 [msec] in the present embodiment).

  In this routine, first, the vehicle speed Vsp detected by the vehicle speed sensor 15 is read in step S1, and the vehicle speed Vsp and the set vehicle speed Va are compared in step S2. The set vehicle speed Va is a vehicle speed that does not cause a rollover even if a sudden operation is performed during traveling. In the present embodiment, the set vehicle speed Va is set to 30 to 40 [Km / h].

  When the vehicle speed Vsp is equal to or lower than the set vehicle speed Va (Vsp ≦ Va), it is determined that there is no possibility of rollover, the process branches to step S3, and both the rapid roll determination flag Flag1 and the rollover flag Flag2 are cleared. (Flag1 ← 0, Flag2 ← 0), the process proceeds to step S4.

  In step S4, based on the steering torque Tq detected by the steering torque sensor 14 and the vehicle speed Vsp detected by the vehicle speed sensor 15, a basic assist amount (torque) τ is set by referring to the basic assist amount map with interpolation calculation. . The characteristics of the basic assist amount map will be described later.

  Thereafter, the process proceeds to step S5, the target assist amount τa is set with the basic assist amount τ (τa ← τ), and the routine is exited.

On the other hand, if it is determined in step S2 that the vehicle speed Vsp of Vsp> Va exceeds the set vehicle speed Va, if excessive steering is performed, there is a possibility of rollover, so the process proceeds to step S6. The roll rate φv detected by the rate sensor 17 is read. Thereafter, in step S7, the roll rate φv [rad / sec ² ] is calculated by time differentiation of the roll rate φv. The process in step S7 corresponds to roll angular acceleration calculation means.

Next, in step S8, the roll angular acceleration φa and the angular acceleration speed determination threshold value α [rad / sec ² ] are compared to check the roll state of the vehicle body. The angular addition speed determination threshold value α is set for each vehicle type according to the center of gravity of the vehicle, the resonance frequency of the vehicle body, and the like. For example, a vehicle with a high vehicle body center of gravity is set to a low value because a rollover is more likely to occur than a vehicle with a low vehicle body gravity center. In the present embodiment, the angular acceleration speed determination threshold value α is set to about 1.1 G (G: gravitational acceleration).

  If it is determined that the roll state of the vehicle body with φa> α changes rapidly, the process proceeds to step S9, the sudden roll determination flag Flag1 is set, and the routine is exited (Flag ← 1). On the other hand, when the roll state of the vehicle body with φa ≦ α changes to a slow roll state that changes at a slow speed, the process proceeds to step S10, the sudden roll determination flag Flag1 is cleared, and the routine exits (Flag ← 0). Note that the processing in step S8 corresponds to roll state determination means.

  The value of the rapid roll determination flag Flag1 is read by the rapid roll assist correction amount setting routine shown in FIG. 4 and the gentle roll assist correction amount setting routine shown in FIG.

  First, the gentle roll assist correction amount setting routine shown in FIG. 4 will be described. This routine is executed every calculation cycle (5 [msec] in this embodiment) slightly longer than the calculation cycle (1 [msec]) of the roll angular velocity flag setting routine described above.

  In step S11, the value of the abrupt roll determination flag Flag1 is referred to. When the flag = 1, the routine proceeds to step S12, and when the flag = 0, the routine is exited.

  When it is determined that the flag = 1 is a rapid roll and the process proceeds to step S12, the count value t1 of the rapid roll control timer counter is incremented (t1 ← t1 + 1), and in step S13, the count value t1 and the validity determination time T1 (this embodiment). Then, a value corresponding to 1 [sec] is compared, and when it is within the validity determination time T1 (T1> t1), the process proceeds to step S14, and when the validity determination time T1 has elapsed (T1 ≦ t1), The process branches to step S15. In step S15, after the sudden roll determination flag Flag1 is cleared (Flag1 ← 0), the routine is exited. Accordingly, Step S14 and subsequent steps are processing within the validity determination time T1.

  In step S14, the roll rate φv detected by the roll rate sensor 17 is read. In step S16, the roll direction and the turning direction of the vehicle body coincide with each other based on the roll rate φv and the roll rate threshold value β. And whether or not a sign of rollover is determined. The roll rate threshold value β is a value that indicates that the possibility of rollover becomes high after a predetermined time has elapsed when exceeding this during turning, and is obtained in advance based on experiments and the like. Note that the roll direction of the vehicle according to the present embodiment is a positive value (+) when the vehicle is turning left, and the roll rate threshold value β is set to a positive value.

  Then, it is determined whether the value obtained by multiplying the roll rate φv and the roll rate threshold value β indicates a positive value or a negative value, and the absolute value of the roll rate φv and the roll rate threshold value β are determined. Compare. As a result, when φv · β ≦ 0 or | φv | ≦ β, it is determined that there is no sign of rollover, the process proceeds to step S17, and a rollover flag Flag2 described later is cleared (Flag2 ← 0). Return to step S12. If φv · β> 0 and | φv |> β, it is determined that there is a sign of rollover, and the process proceeds to step S18.

  Multiplying the roll rate φv and the roll rate threshold value β makes it possible to determine whether or not the turning direction of the vehicle matches the roll direction. That is, in the case of φv · β> 0, it indicates that the turning direction of the vehicle and the roll direction coincide. In addition, φv · β ≦ 0 indicates a state in which the vehicle body of the vehicle that is turning is rolling toward the turning inner wheel, and therefore, the lateral acceleration and the roll acceleration that occur during turning are cancelled. On the other hand, when the absolute value of the roll rate φv exceeds the roll rate threshold value β, it indicates a rollover sign (behavior leading to rollover).

  Therefore, a rollover sign can be detected by examining the product of the roll rate φv and the roll rate threshold β and the comparison result between the absolute value of the roll rate φv and the roll rate threshold β. . Note that the processing in step S16 corresponds to roll rate determination means for determining whether or not a rollover sign has been detected.

  Then, when it is determined that there is a sign of rollover of φv · β> 0 and | φv |> β and the process proceeds to step S18, the rollover flag Flag2 is set (Flag2 ← 1), and rollover is performed in step S19. The count value t2 of the predictive timer counter is incremented (t2 ← t2 + 1), and the count value t2 is compared with the holding time T2 in step S20.

  By the way, at the stage of a sign that the vehicle turning is indicating rollover, first, the roll rate φv is greatly changed, and then the lateral acceleration Gy is slowly increased. The holding time T2 is a waiting time until the roll angular acceleration φa is detected, and in this embodiment, T2 = 0.01 [sec].

When the holding time T2 has not been reached (T2> t2), the process returns to step S12 via step S17. On the other hand, when the holding time T2 is reached (T2 ≦ t2), the process proceeds to step S21, and the lateral acceleration Gy detected by the lateral acceleration sensor 16 is read. In step S22, the absolute value | Gy | The set lateral acceleration judgment threshold value ξ is compared. This lateral acceleration determination threshold value ξ is a value indicating that the possibility of a rollover increases when the lateral acceleration Gy exceeds the lateral acceleration determination threshold value ξ, and is obtained based on experiments or the like in advance. Yes. In this embodiment, ξ is set to about 5 to 10 [m / S ² ]. Further, the processing in step S22 corresponds to lateral acceleration determination means.

  When | Gy | ≦ ξ, there is no possibility of rollover, so the process returns to step S12 via step S17. Further, when | Gy |> ξ, that is, when | Gy |> ξ in a state where | φv |> β is maintained, rollover may occur. Based on the rate φv, the correction assist amount (torque) τ assist is set, the correction assist amount τ assist is set by referring to the correction assist amount setting table with interpolation calculation, and the process proceeds to step S24. Note that the processing in step S23 corresponds to a correction assist amount calculation means during sudden rolls.

  FIG. 7 shows the characteristic of the correction assist amount τaist stored in the correction assist amount setting table. As shown in the figure, the correction assist amount τaist has a point-symmetric nonlinear characteristic with a negative value (right turn) and a positive value (left turn), with the contact piece being zero, The assist amount τasist gradually increases as the roll rate φv increases during turning. In this case, when the corrected assist amount τasist is larger than a basic assist amount τ described later (| τasist |> | τ |), a reverse assist state in which an assist amount opposite to the steering direction of the steering wheel 4 is given. Become. The characteristics of the correction assist amount τassis stored in the correction assist amount setting table are different for each vehicle type. That is, for example, a high center of gravity vehicle such as a one-box vehicle is more likely to cause rollover than a low center of gravity vehicle such as a sports car, and therefore, the amount of change with respect to the roll rate φv is set to be large.

  In step S24, based on the steering torque Tq detected by the steering torque sensor 14 and the vehicle speed Vsp detected by the vehicle speed sensor 15, the basic assist amount (torque) τ is set with reference to the basic assist amount map.

  As shown in FIG. 9, the basic assist amount map is set to have such characteristics that the basic assist amount τ increases as the vehicle speed Vsp decreases or the steering torque Tq increases, and the steering torque Tq is 0. In the vicinity shown, a dead zone in which the basic assist amount τ is 0 is set. Therefore, in this basic assist amount map, as the steering torque Tq increases, in other words, as the steering wheel 4 becomes heavier, the steering assist force increases and steering becomes easier. The basic assist amount τ may be obtained by a calculation formula using the steering torque Tq and the vehicle speed Vsp as parameters.

In step S25, the target assist amount (torque) τa is calculated from the following equation based on the target assist amount τa and the correction assist amount τaist (correction gain), and the routine is exited. The processing in step S25 corresponds to a sudden roll target assist amount calculation means.
τa ← τ−τasist

  In the gentle roll assist correction amount setting routine shown in FIG. 5 described later, the correction assist amount τ assist is multiplied by the correction gain A set based on the roll rate φv, and the value is subtracted from the basic assist amount τ. . Therefore, the target assist amount τa set in the gentle roll assist correction amount setting routine becomes larger than the target assist amount τa set in the sudden roll assist correction amount setting routine as the roll rate φv is decreased. The target assist amount τa is read by a target assist current setting routine shown in FIG. This target assist current setting routine will be described later.

  Thus, in the present embodiment, φv> from the time when the sudden roll determination flag Flag1 is set (Flag1 = 1) until the validity determination time T1 (1 [sec] in the present embodiment) elapses. When the state of β continues for the holding time T2 (0.01 [sec] in this embodiment) and the lateral acceleration Gy exceeds the lateral acceleration determination threshold value ξ, the target assist amount τa is limited. Therefore, it is possible to prevent a delay in starting the control at the time of sudden steering.

  Further, by limiting the target assist amount τa at this time by the correction assist amount τaist set based on the roll rate φv, a reaction force corresponding to the roll rate φv is applied to the steering wheel 4 and correction is performed. When the assist amount τ assist exceeds the basic assist amount τ, an assist amount (reverse assist torque) opposite to the steering direction is applied, so that the steering in the turning direction is positively restricted and the rollover is prevented. It can be surely avoided.

  In this case, instead of monitoring by time in the process in step S20, a value (integrated value) obtained by integrating the roll rate φv with time is monitored, and the lateral acceleration Gy is determined as a lateral acceleration every time the integrated value reaches a predetermined value. By examining whether or not the threshold value ξ is exceeded, it is possible to effectively cope with a sudden change in roll rate.

  Next, processing of the gentle roll assist correction amount setting routine shown in FIG. 5 will be described. Since this routine has many parts in common with the processes after step S14 of the above-described sudden roll assist correction amount setting routine, the description of the parts in which the common processes are executed will be simplified.

  This routine is executed every calculation cycle (5 [msec] in this embodiment) slightly longer than the calculation cycle (1 [msec]) of the roll angular velocity flag setting routine described above. First, in step S31, the value of the sudden roll determination flag Flag1 is referred to. When the flag = 0 is a slow roll, the process proceeds to step S32. When Flag = 0 is a slow roll, the routine is directly exited.

  In step S32, the roll rate φv detected by the roll rate sensor 17 is read. In step S33, based on the roll rate φv and the above-described roll rate threshold value β, the roll direction and the turning direction of the vehicle body are equal. A determination is made as to whether or not a rollover has occurred, and the possibility of rollover is determined.

  When φv · β> 0 and | φv |> β, since there is a sign of rollover, the process proceeds to step S34. If φv · β ≦ 0 or | φv | ≦ β, no rollover sign is detected, so the process proceeds to step S35, the rollover flag Flag2 is cleared (Flag2 ← 0), and the routine is exited.

  If it is determined that there is a sign of rollover and the process proceeds to step S34, the rollover flag Flag2 is set (Flag2 ← 1), and the count value t2 of the rollover sign timer counter is incremented at step S36 (t2 ← t2 + 1). In step S37, the count value t2 is compared with the holding time T2. As described above, at the stage where the turning vehicle is in a sign of rollover, first, the roll rate φv changes greatly, and then the lateral acceleration Gy is slowly increased. The holding time T2 is a waiting time until the roll angular acceleration φa is detected (T2 = 0.01 [sec] in the present embodiment).

When the holding time T2 has not been reached (T2> t2), the routine is directly exited. On the other hand, when the holding time T2 is reached (T2 ≦ t2), the process proceeds to step S38, the lateral acceleration Gy detected by the lateral acceleration sensor 16 is read, and in step S39, the absolute value | Gy | The set lateral acceleration judgment threshold value ξ is compared. This lateral acceleration judgment threshold value ξ is a value indicating that the possibility of rollover increases when the lateral acceleration Gy exceeds the lateral acceleration judgment threshold value ξ (in this embodiment, 5 to 10 [m / S ² ]).

  When | Gy | ≦ ξ, there is no possibility of rollover, so the routine is exited. Further, when | Gy |> ξ, that is, when | Gy |> ξ in a state where | φv |> β is maintained, rollover may occur. Based on the rate φv, the correction assist amount (torque) τ assist is set by referring to the correction assist amount setting table shown in FIG. 7 with interpolation calculation. Further, the correction gain A is set by referring to the correction gain table shown in FIG. 8 with interpolation calculation. Since the characteristics of the correction assist amount τ assist stored in the correction assist amount setting table shown in FIG. The processing in step S40 corresponds to a slow roll correction value calculation means.

  The correction gain A stored in the correction gain table shown in FIG. 8 has an inverted triangular linear characteristic in which the contact piece is 0 when the roll rate φv is 0. Therefore, the correction gain A increases as the roll rate φv during the turning operation increases. The maximum value of the correction gain A is 1 (that is, 100 [%]).

  Thereafter, when the process proceeds to step S41, based on the steering torque Tq detected by the steering torque sensor 14 and the vehicle speed Vsp, the basic assist amount map shown in FIG. ) Set τ. The basic assist amount τ may be obtained from a calculation formula using the steering torque Tq and the vehicle speed Vsp as parameters.

Thereafter, in step S42, the target assist amount τa is calculated based on the basic assist amount τ, the correction gain A, and the correction assist amount τassis, and the routine is exited. Note that the processing in step S42 corresponds to a slow roll target assist amount calculation means.
τa ← τ−A ・ τasist

  In this way, in the slow roll assist correction amount setting routine, the correction assist amount τassis is multiplied by the correction gain A, so the calculated target assist amount τa is the target assist amount obtained in the sudden roll assist correction amount setting routine. The value is larger than τa, and accordingly, the reaction force received by the driver during the steering operation is reduced. In other words, it becomes heavier than the normal assist amount, which can inform the driver of a rollover sign.

  The target assist amount τa set by the roll angular velocity flag setting routine of FIG. 3, the sudden roll assist correction amount setting routine of FIG. 4, or the gentle roll assist correction amount setting routine of FIG. 5 is set as the target assist current setting shown in FIG. Read by routine.

  In this routine, first, in step S51, the target assist amount τa is read. In subsequent step S52, the target assist current P corresponding to the target assist amount τa is set, and the routine is exited.

  The motor control unit 22 calculates a difference ΔP (ΔP ← P−Is) between the target assist current P and the motor current Is detected by the current detection unit 25 and supplied to the electric motor 13, and the difference ΔP becomes 0. A control signal (feedback control signal) D that converges is generated by proportional-integral control or the like, and is output to the motor drive signal generation circuit 23. The motor drive signal generation circuit 23 generates a motor drive signal (for example, a PWM signal) corresponding to the control signal D output from the motor control unit 22 and outputs it to the motor drive circuit 24.

  The motor drive circuit 24 supplies the electric motor 13 with a voltage having a magnitude and direction corresponding to the current flowing by the voltage according to the motor drive signal generated by the motor drive signal generation circuit 23. Then, the driving force of the electric motor 13 is transmitted to the pinion shaft 5 via the assist transmission mechanism 12.

  When the vehicle speed Vsp is equal to or lower than the set vehicle speed Va, the target assist amount τa is set by the basic assist amount τ, and thus the electric motor 13 is driven with a driving force corresponding to the target assist current P. Therefore, the steering torque applied to the steering wheel 4 is assisted by the electric motor 13, and the driver's load during steering is reduced.

  On the other hand, as a result of, for example, a running vehicle making a sudden turn in an overspeed state (so-called J-turn) or turning the steering wheel abruptly like a fishhook turn, the roll angular acceleration φa becomes an angular acceleration determination threshold value. When α is exceeded (φa> α), the behavior of the vehicle is monitored from the moment during the validity determination time T1 (1 [sec] in the present embodiment). Then, with the absolute value | φv | of the roll rate φv continuing the roll rate threshold value β for the holding time T2 (0.01 [SEC] in the present embodiment), the lateral acceleration Gy is the lateral acceleration determination threshold value. When ξ is exceeded, the correction assist amount τ assist is set based on the roll rate φv.

  Since the target assist amount τa is set as a value obtained by subtracting the correction assist amount τasist from the basic assist amount τ (τa ← τ−τasist), the roll rate φv is increased (a plus direction for a left turn and a minus direction for a right turn). ), The amount of assist applied to the steering wheel 4 is reduced with non-linear characteristics. As a result, when the roll angular acceleration φa exceeds the angular acceleration determination threshold value α, a reaction force is applied to the steering wheel 4 quickly, and rollover can be effectively avoided. In this case, when the correction assist amount τist exceeds the basic assist amount τ, the target assist amount τa is in the opposite direction to the steering direction, the reverse assist torque is applied to the steering wheel 4, and the steering in the turning direction is actively restricted. Therefore, rollover can be avoided more reliably.

  When the roll angular acceleration φa is equal to or less than the angular acceleration determination threshold α (φa ≦ α), the basic assist amount τ is subtracted by a value obtained by multiplying the correction assist amount τist by the correction gain A to obtain the target assist amount τa. Is calculated (τa ← τ−A · τasist), the target assist amount τa is larger than the target assist amount τa set in the above-described sudden roll assist correction amount setting routine. Sometimes, the reaction force received by the driver is small, and the driver can be notified of a rollover sign.

  Thus, in this embodiment, when a rollover sign is detected, the assist amount generated by driving the electric motor 13 is limited, and the roll reaction is suppressed by relatively increasing the steering reaction force. Since this is done, even if the vehicle is not equipped with a braking system and the rollover cannot be avoided by the braking system, this embodiment can be used as long as the vehicle is equipped with the electric power steering device 1. By applying, rollover can be easily avoided.

  At that time, when the roll angular acceleration φa exceeds the angular acceleration determination threshold value α, the target assist amount τa is smaller than that when the angular acceleration determination threshold value α does not exceed, or the reverse assist is performed. Set as torque. As a result, the reaction force applied to the steering wheel 4 increases, so that rollover can be effectively avoided. On the other hand, when the roll angular acceleration φa is lower than the angular acceleration determination threshold value α, the basic assist amount τ is decreased by the value obtained by multiplying the correction assist amount τist by the correction gain A. The applied reaction force becomes moderate, and the driver can be warned that there is a sign of rollover.

  In addition, since rollover is avoided by steering by the electric power steering apparatus 1, not only can a sign of rollover be promptly transmitted to the driver, but also the braking outer wheel is controlled by the braking system. Compared with the case where rollover is avoided by applying power, the tire grip force of the turning outer wheel can be ensured, so that rollover can be avoided while the vehicle behavior is stabilized.

  Further, in the abrupt roll assist correction amount setting routine, control is performed to decrease the target assist amount τa only during the effective determination time T1 after the roll angular acceleration φa exceeds the angular addition speed determination angular acceleration determination threshold value α. Since this is done, there is no continuous reaction force more than necessary.

  Further, when setting the correction assist amount τaist, the roll angular acceleration φa, the holding time T2, the lateral acceleration Gy, and the respective values are monitored. Suppression can be controlled with high accuracy.

  The present invention is not limited to the above-described embodiment. For example, the system according to the present invention can be applied to a vehicle equipped with a braking system. By adopting this system in a vehicle equipped with a braking system, braking can be performed. Prior to the rollover avoiding operation by the system, the rollover can be avoided by steering. As a result, rollover can be avoided in stages by controlling different systems. The assist actuator is not limited to the electric motor 13 and may be a hydraulic motor.

Schematic of a vehicle equipped with a rollover suppression control device Circuit block diagram of motor control unit Flowchart showing a roll angular velocity flag setting routine Flowchart showing a sudden roll assist correction amount setting routine Flowchart showing a gentle roll assist correction amount setting routine Flow chart showing a target assist current setting routine Explanatory drawing showing the characteristics of the correction assist amount setting table Explanatory diagram showing the characteristics of the correction gain table Explanatory diagram showing the characteristics of the basic assist amount map

Explanation of symbols

1 ... Electric power steering device,
4 ... Steering wheel,
13: Electric motor,
14: Steering torque sensor,
15 ... Vehicle speed sensor
16 ... Lateral acceleration sensor,
17 ... Roll rate sensor,
21 ... Motor control unit,
22 ... motor control unit,
25 ... current detector,
α: Angular addition speed judgment threshold,
β… Roll rate threshold,
ξ ... Threshold value for judging lateral acceleration,
τ ... Basic assist amount,
τa: Target assist amount,
τasist: correction assist amount,
φa: Roll angular acceleration,
φv: Roll rate,
A: Correction gain,
Flag1 ... sudden roll determination flag,
Flag2 ... Rollover flag,
Gy ... Lateral acceleration,
T1 ... Validity judgment time,
T2: Holding time,
Tq: Steering torque,
Vsp ... Vehicle speed,

Claims (4)

An assist actuator for assisting a steering torque applied to the steering wheel, a roll rate detecting means for detecting a roll rate of the vehicle body, a steering torque detecting means for detecting the steering torque, and at least the steering torque detected by the steering torque detecting means And a control means for setting a target assist amount for driving the assist actuator by correcting the basic assist amount based on the basic assist amount,
The control means includes
Roll angular acceleration calculating means for calculating the roll angular acceleration of the vehicle body based on the roll rate;
Roll state determining means for determining whether the roll state of the vehicle body changes rapidly or slowly based on the roll angular acceleration;
Roll rate determination means for comparing the roll rate with a roll rate threshold value to determine whether or not there is a sign of rollover;
A correction assist that corrects in a direction to decrease the target assist amount based on the roll rate when the roll state determination unit determines that the roll is sudden and the roll rate determination unit determines that there is a sign of rollover. A correction assist amount calculation means during a sudden roll for calculating a correction amount;
A rollover suppression control device for a vehicle, comprising: a sudden roll target assist amount calculating means for calculating the target assist amount by correcting the basic assist amount with the correction assist amount. An assist actuator for assisting steering torque applied to the steering wheel; roll rate detection means for detecting a roll rate of the vehicle body; steering torque detection means for detecting the steering torque; and lateral acceleration detection means for detecting lateral acceleration of the vehicle body; A control means for calculating a basic assist amount based on at least the steering torque detected by the steering torque detecting means, and for setting the target assist amount for driving the assist actuator by correcting the basic assist amount;
The control means includes
Roll angular acceleration calculating means for calculating the roll angular acceleration of the vehicle body based on the roll rate;
Roll state determining means for determining whether the roll state of the vehicle body changes rapidly or slowly based on the roll angular acceleration;
Roll rate determination means for comparing the roll rate with a roll rate threshold value to determine whether or not there is a sign of rollover;
When the roll state determination means determines that the roll is sudden and the roll rate determination means determines that there is a sign of rollover, the lateral acceleration and the lateral acceleration threshold value are compared to further indicate a rollover sign. Lateral acceleration determining means for determining whether or not there is,
When the lateral acceleration determining means determines that there is a sign of rollover, a sudden roll correction assist amount calculating means for calculating a correction assist correction amount for correcting the target assist amount in a direction to decrease based on the roll rate; ,
A rollover suppression control device for a vehicle, comprising: a sudden roll target assist amount calculating means for calculating the target assist amount by correcting the basic assist amount with the correction assist amount. When the roll acceleration determination unit determines that the roll acceleration determination unit determines that there is a sudden roll state, and the roll rate determination unit determines that there is a sign of rollover, 3. The vehicle roll according to claim 2, wherein when the set holding time is continued, the lateral acceleration is compared with a lateral acceleration threshold value to determine whether or not there is a sign of rollover. Over suppression control device. The control means includes
When it is determined that the roll state determination unit is in the slow roll state and the roll rate determination unit determines that there is a sign of rollover, based on the roll rate, the correction assist correction amount and the correction assist correction amount Slow roll correction value calculation means for calculating the correction gain,
2. A slow roll target assist amount calculating means for calculating the target assist amount by correcting the basic assist amount by a value obtained by multiplying the correction assist amount by the correction gain. The rollover suppression control device for a vehicle according to any one of?

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